The subject of the invention described below is a device for a Jacquard machine for lifting the pile warp threads into one of three possible positions for the purpose of forming the shed in a face-to-face weaving machine, and this for each weft insertion. This invention relates more particularly to a device which, connected at one side to the hooks and at the other to one or more of the warp threads, can achieve three possible positions of the warp threads connected thereto.
A Jacquard machine of the known type is in fact provided with at least one arrangement of two complementary rows of hooks, in which in a first possibility each hook--depending on the complementary row to which it belongs--can be carried along by one of two knives moving up and down in opposite phase, and can move along with the up and down moving knife on which it rests with a projecting part, or in a second possibility can be held by means of known selection mechanisms in its top or its bottom position--depending on the design of the Jacquard machine--while the knife carries out the normal up and down movement. Two hooks situated directly opposite each other and belonging to a different complementary row form a so-called complementary hook set, each either moving with their respective knives in opposite phase to each other, or of which one hook--or both hooks--can be selected in its (their) top (possibly bottom) position.
For the weaving of certain weaves in face-to-face pile weaves it must be possible for the pile warp threads to be lifted in three possible positions. In the case of certain weaves these three possibilities for the positions do not have to be present simultaneously on each shot, but it can be sufficient to achieve two positions on the first pick and two other positions on the second pick, so that after these 2 weft insertions the three necessary positions of the warp thread have been achieved. The required selection possibilities in the case of such weaves are illustrated with reference to the appended FIG. 1, which shows schematically a double-shuttle woven face-to-face 2-shot V weave. The three possible positions of the pile warp threads are indicated below by top (T), bottom (B) and middle (M).
The weft threads in the bottom weave are indicated by the letters WB, and the weft threads in the top weave are indicated by the letters WT. In a double-shuttle woven fabric, 2 wefts are simultaneously inserted threads per pick--one in the top fabric (TW), and one in the bottom fabric (BW). The first to the 6th pick has been indicated vertically below that on the figure by means of a serial number (1 to 6).
The two backing fabrics comprise binder warp threads (7) and (7') and (8) and (8') respectively and tight warp threads (9) and (10) respectively.
In addition, the pile warp threads forming the pile are woven between the two backing fabrics which are held at a certain distance from each other, while the dead pile warp threads are bound into either the top fabric or the bottom fabric. Depending on the pattern (the color) which one wishes to obtain in the fabric, a pile warp thread until then forming the pile is bound into the top fabric or bottom weave at a particular weft insertion, and a pile warp thread which has been dead until then can begin to form pile at a particular weft insertion.
The five pile warp threads are indicated in FIG. 1 by P1, P2, P3, P4 and P5. The pile warp threads P1, P2, P3 are provided for binding into the bottom weave. The pile warp threads P4, P5 are provided for binding into the top weave. The three necessary positions of the pile warp threads can be indicated as follows in the figure:
"Bottom" position: the pile warp threads are situated below weft WB of the bottom fabric PA0 "Top" position: the pile warp threads are situated above weft WT of the top fabric PA0 "Middle" position: the pile warp threads are situated between WB and WT. PA0 Each odd pick/s "bottom" or "middle" PA0 Each even pick/s "bottom" or "top". PA0 Each odd pick/s "bottom" or "top" PA0 Each even pick/s "top" or "middle".
The pile warp threads P1, P2, P3 must be able to be lifted in the following positions:
In pick/s 1 to 6 the pile warp thread P1 is lifted in succession, to the following positions: bottom - top - bottom - top - middle - bottom.
The pile warp threads P4, P5, are lifted in the following positions:
Thus, for example, for pick/s 1 to 6 pile warp thread P5 is lifted in succession to the following positions: top - middle - top - middle - bottom - top.
For each pick/s there consequently has to be the choice between two possible positions of the pile warp threads, while through mutual combination over two pick/s a total of three possible positions have to be provided for every two pick/s. By selection of the hooks, in cooperation with the device to which this invention relates, it must be possible to have either the choice between the positions "bottom" and "middle" or the positions "bottom" and "top", or the positions "top" and "middle" for each pick/s. In the case of the example described above it is even necessary for the required selection possibilities of a particular group of pile warp threads (P1, P2, P3) not to correspond to those of another group of pile warp threads (P4, P5), so that the device in question here will have to be present in two possible embodiments on one Jacquard machine.
A possible embodiment of a known device for achieving the selection possibilities described above makes use of a pulley arrangement comprising three pulley elements, and is illustrated with reference to FIG. 2, which is appended hereto. Each pulley element (1), (2), (3) comprises two rotatable rollers (1'), (1"); (2'), (2") and (3'), (3") which are fixed to each other one above the other and in the same plane by a mechanical connection of their shafts. Each warp thread is now connected by means of the harness cord to the bottom end (4') of a pulley cord (4). Tackle cord (4) runs over the bottom roller (3") of the bottom pulley element (3) and is directed back downwards with the other end connected to a fixed or movable (controllable) point or grid (5). The top pulley roller (3') of pulley element (3) hangs in the loop which is formed by another pulley cord (6) which is hanging down, and of which both ends each lie higher up over one of two bottom pulley rollers (1") and (2")--or of pulley elements (1) and (2) hanging at the same height--and are fixed, directed back downwards, each in a fixed point. The top pulley rollers (1') and (2') of the above-mentioned pulley elements (1) and (2) each hang in the loop formed by downward-hanging pulley cords (7) and (8), while each end of each tackle cord (7) and (8) is fixed higher up to one hook of a set of two complementary hooks (9) and (10), and (9') and (10') respectively.
Assuming that the Jacquard machine is equipped to select the hooks (9), (9'), (10), (10') in their top position, we can describe how this known device works as follows:
If no hook at all is selected, then the hooks move up and down in opposite phase to each other, and the pulley elements (1) and (2) then remain hanging at the same height, since each pulley element is suspended in the downward-hanging loop of a cord (7), (8) of which one end moves up and the other end moves down in opposite phase to each other. There is no upward or downward movement of pulley elements at all (only the pulley cords (7) and (8) move to and fro over the rollers (1') and (2')), and the end (4') of tackle cord (4) remains in the "bottom" position.
If one of the hooks, for example hook (9), has been selected in its top position, then in the next phase of the hook movement hook (10) is moved upwards over a distance (h) (=lifting of the knives), and pulley element (1) is raised over half that distance: h/2. Pulley element (2) is in the preceding situation, since neither hook (9') nor hook (10') have been selected, and pulley element (2) remains hanging at the same height. Through the lifting of pulley element (1) over a height (h/2), each pulley element (3) is raised over that distance, which results in a raising of the end (4') of tackle element (4) over a distance (h). The warp threads connected to it are taken into the "middle" position.
If now, for example, the hooks (9) and (9') have been selected, then the hooks (10) and (10') in the subsequent movement phase are moved up over a distance (h), as a result of which both pulley element (1) and pulley element (2) move upwards over a height (h/2). Pulley element (3) thereby undergoes a lifting over a distance (h), as a result of which the bottom end (4') of pulley element (4) is pulled upwards over a distance (2h). The warp threads connected to it are taken into the "top" position. Consequently, for each pick the warp threads can be lifted to one of the three possible positions by selecting none, one, or two of the hooks (9), (10) or (9'), (10').
The disadvantage of this known device lies in the fact that for obtaining these selection possibilities two sets of complementary hooks (9), (10) and (9'), (10') are needed, in conjunction with the pulley arrangement of FIG. 2.